URL parameter "format=html" causes an error "options.render is not a function"

[is2ei]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

3.29.0

Plugin version

5.0.2

Node.js version

16.14.2

Operating system

Linux

Operating system version (i.e. 20.04, 11.3, 10)

20.04.0

Description

The option list.format=html requires list.render.

https://github.com/fastify/fastify-static#listformat

Directory list can be also in html format; in that case, list.render function is required.

The problem is that it is possible to pass list.format=html using the URL parameter even though list.render option is not given.

Steps to Reproduce

1. Register @fastify/static with list: true.
2. Access the URL with query parameter ?format=html.
3. You will see an error.

short example:

const fastify = require('fastify')();
const path = require('path');

fastify.register(require('@fastify/static'), {
  root: path.join(__dirname, 'public'),
  index: false,
  list: true,
});

fastify.listen(3000);

error example:

{"statusCode":500,"error":"Internal Server Error","message":"options.render is not a function"}

I created an example on stackblitz: https://stackblitz.com/edit/node-hdvl2e?file=index.js

Expected Behavior

I guess we have some options.

• Allowing list.render with list.format=json.
• Disabling ?format=html in URL parameter.
• Documenting not to use ?format=html.

[mcollina]

I think the first option is the way to go.